Stroboscopic Effect Research Articles

Solution to Some Key Problems of Self-exciting Electronic Ballast

Self-exciting electronic ballast, of small size, and low cost, and high power, with no stroboscopic effect, no noise, is widely used in the general lighting market. This paper describes the cause of high switching loss of self-exciting electronic ballast, based on its operational principle; then, to reduce the switch temperature and increase the reliability of the product, the drive circuit has been improved, to achieve soft-switching. The theory analysis, simulation and experimental result prove the feasibility and compatibility of this new method in practice. Finally, the design procedure and winding method of the self-exciting current transformer are introduced.

The effect of various levels of stroboscopic illumination on the growth of guinea pig eyes

BackgroundThe aim was to investigate various levels of stroboscopic illumination effect on the growth of guinea pig eyes.MethodsThirty‐six two‐week‐old guinea pigs were randomised to one of three treatment groups (n = 12 for each). Two stroboscopic‐reared groups were raised with a duty diurnal cycle of 50 per cent at a flash rate of 0.5-Hz. Illumination intensity varied between zero‐to‐250 lux or zero‐to‐500 lux during each cycle in each group, respectively. The third control group was exposed to 250 lux illumination. Refraction and biometric measurements were taken for each animal prior to and after two, four, six and eight weeks of treatment. Finally, retinal microstructure was examined.ResultsThere was significant correlation between refractive errors and axial elongation. After eight weeks of treatment, illumination with flickering light 0–250 lux caused a larger myopic shift with increased axial length than illumination of continuous 250 lux. Stroboscopic illumination with zero‐to‐500 lux caused a further myopic shift and longer axial length than stroboscopic illumination with zero‐to‐250 lux. In animals raised in flickering light of zero‐to‐250 lux or zero‐to‐500 lux for eight weeks, the outer segment disc membranes in photoreceptor layers were found deformed and detached.ConclusionChronic exposure to low‐frequency temporally modulated illumination‐induced histological damage in the retina and induced exaggerated axial length elongation.

Looking with the ears – Tom Stoppard’s Artist Descending a Staircase

Artist Descending a Staircase is a radio drama in which Tom Stoppard makes an intertextual reference to the famous cubist painting of Marcel Duchamp – The Nude Descending a Staircase. Duchamp aimed not only at representing three dimensionality of the object on the two dimensional canvass (which was the attempt common to all the cubists) but also the notion of movement by means of a stroboscopic effect. Tom Stoppard, working in a different medium, tries to represent reality by means of the radio medium. In the process he invites the listeners to actively participate in the process of creating meaning. He sets yet another ambush for the listeners and makes them discover that the tape recording heard by them at the beginning and end of the play does not present a murder (as the characters of this short radio play assume) but an accident – Donner was not killed by one of his friends but fell down the stairs while chasing a fl y which was destroying Beauchamp’s tape of silence.

Strobes: Pyrotechnic Compositions That Show a Curious Oscillatory Combustion

Strobes are pyrotechnic compositions which show an oscillatory combustion; a dark phase and a flash phase alternate periodically. The strobe effect has applications in various fields, most notably in the fireworks industry and in the military area. All strobe compositions mentioned in the literature were discovered by trial and error methods and the mechanisms involved remain unclear. Many oscillatory systems such as Belousov-Zhabotinsky reactions, cool flames, self-propagating high-temperature synthesis have been observed and theories developed to elucidate their unstable behavior based on chemical interactions or based on physical processes. These systems are compared to experimental observations made on strobe mixtures.

Risk assessment for LED lighting flicker

BackgroundLED (Light Emitting Diode) based lighting has been predicted to reach as much as 60% share of the global lighting market in the next 10 years. It is characterized by...

Correlation Based Visual Motion Detection Algorithm with Stroboscopic Effect Elimination

Correlation Based Visual Motion Detection Algorithm with Stroboscopic Effect Elimination

Optoelectronic stroboscopic system for measurement of the frequency of harmonic vibrations based on the use of a genetic algorithm

Principles underlying the design of optoelectronic measurement systems based on the use of a genetic algorithm are presented. A method and means of measuring the frequency of a harmonic vibration, where detection of a stroboscopic effect by means of a high-speed video camera serves as the measurement criterion, are proposed. Optimization of the search for the vibration frequency in the image of a test object is performed by means of a genetic algorithm.

THE HOT-JUPITER KEPLER-17b: DISCOVERY, OBLIQUITY FROM STROBOSCOPIC STARSPOTS, AND ATMOSPHERIC CHARACTERIZATION

This paper reports the discovery and characterization of the transiting hot giant exoplanet Kepler-17b. The planet has an orbital period of 1.486 days, and radial velocity measurements from the Hobby-Eberly Telescope (HET) show a Doppler signal of 420+/-15 m.s-1. From a transit-based estimate of the host star's mean density, combined with an estimate of the stellar effective temperature T_eff=5630+/-100 K from high-resolution spectra, we infer a stellar host mass of 1.061+/-0.067 M_sun and a stellar radius of 1.019+/-0.033 R_jup. We estimate the planet mass and radius to be Mp=2.450+/-0.114 M_jup and Rp=1.312+/-0.018 R_jup and a planet density near 1.35 g.cm-3. The host star is active, with dark spots that are frequently occulted by the planet. The continuous monitoring of the star reveals a stellar rotation period of 11.89 days, 8 times the the planet's orbital period; this period ratio produces stroboscopic effects on the occulted starspots. The temporal pattern of these spot-crossing events shows that the planet's orbit is prograde and the star's obliquity is smaller than 15 deg. We detected planetary occultations of Kepler-17b with both the Kepler and Spitzer Space Telescopes. We use these observations to constrain the eccentricity, e, and find that it is consistent with a circular orbit (e<0.0011). The brightness temperatures of the planet the infrared bandpasses are T_3.6um=1880+/-100 K and T4.5um=1770+/-150 K. We measure the optical geometric albedo A_g in the Kepler bandpass and find A_g = 0.10+/-0.02. The observations are best described by atmospheric models for which most of the incident energy is re-radiated away from the day side.

Detection and acceptability of stroboscopic effects from flicker

Previous studies have demonstrated that the perception of stroboscopic effects from flickering light is strongly influenced by both the frequency and the amount of modulation (e.g. percent flicker). The relationship, if any, between these factors for the detection and acceptability of stroboscopic effects has not been elucidated under conditions corresponding to illuminating engineering practice. In a laboratory study, participants reported whether they could detect stroboscopic effects from flickering light with a range of frequencies and percent flicker values, and if detected, whether it was acceptable. The resulting data can provide functional relationships between frequency and percent flicker in terms of detection and acceptability of stroboscopic effects under conditions corresponding to those tested.

Effects of flicker characteristics from solid-state lighting on detection, acceptability and comfort

A study to assess the detection and acceptability of flicker and stroboscopic effects under different lighting conditions was conducted. Frequencies from 50 Hz to 300 Hz were assessed, as well as different modulation amounts, duty cycles, waveform shapes and correlated colour temperatures. For the range of conditions evaluated, direct perception of flicker was negligible at 100 Hz or higher, but stroboscopic effects could be perceived at 300 Hz. Reducing flicker modulation from 100% to 33% decreased perception of stroboscopic effects. A higher duty cycle was associated with slightly lower discomfort. The implications for solid-state lighting systems producing high-modulation flicker are discussed.

Design of a fast rotational chopper for X-ray pump–probe experiments at Diamond Light Source

New trends in X-ray crystallography are concerned with the study of transient conditions of atomic structures, which take place after an energy activation agent is introduced. These time-resolved experiments require a fast mechanical shutter to interrupt the X-ray beam in a pump–probe cycle, with the aim to generate a stroboscopic effect. Thus, only diffraction data that are representative of the activated structure are actually collected. A rotating type of shutter, also known as chopper, is presented with the purpose to enable time-resolved experiments to be performed at I19 small-molecule single-crystal diffraction beamline. Exceptional stability in the rotational speed is critical to achieve the desired stroboscopic effect with minimum jitter. This requirement can be addressed only through design by the specification of suitable components and implementation of high-precision methods in manufacturing. The proposed equipment is comprised of a spindle supported on air bearings coupled to a slotted disc rotating inside a vacuum enclosure and driven by a brushless servo motor. Advanced control features are proposed to ensure that speed stability is achieved. Preliminary tests produced very encouraging results, giving strong indication that the chopper satisfies the specifications required for time-resolved experiments.

Study of intra-subject random variations of stabilometric parameters

This study of intra-subject random variations of stabilometric parameters was achieved in the context of the standardized clinical stabilometry, in use in France and Southern Europe since 1985. The outstanding interest of stabilometry to follow up patients makes the results of this study indispensable for clinicians and their international publication is particularly important as, these days, the standardization Committee for clinical stabilometry resumes its work within the International Society for Postural and Gait Research. Such a study is possible only on the topological stabilometric parameters because of the stroboscopic effect on the dynamic parameters of the sampling rate of our computerized measuring chains.

Headwinds to a Clean Energy Future: Nuisance Suits against Wind Energy Projects in the United States

In recent years, opponents of wind energy projects have begun employing the common and statutory law of nuisance to delay and restrict the construction of wind power developments in their neighborhoods and in nearby regions. The case law on this subject is limited, but opponents of wind developments have filed nuisance suits due to various concerns: the noise created by wind turbines; the flicker or strobe effect created when light from the rising or setting sun hits the turbine blades; the danger posed by thrown blades, ice, or collapsing towers; the unsightly or aesthetically displeasing nature of wind turbines; and

P‐30: Temporal Sampling Parameters and Motion Portrayal of Television

AbstractThe relationship between the temporal sampling parameters and motion portrayal of television images was studied. Subjective evaluation tests revealed the parameter values for perceptible and acceptable limits of motion blur. The stroboscopic effect was also evaluated for various sampling frequency and aperture by using the test materials similar to those used in broadcast programs.

Pulfrich phenomena are coded effectively by a joint motion-disparity process

Pulfrich phenomena are a class of depth illusions generated by an interocular time delay. This may be demonstrated with continuously moving stimuli, stroboscopic displays undergoing apparent motion, or dynamic noise patterns. Previous studies suggest that neurons jointly tuned to motion and disparity may be responsible for the phenomena. Model cells with such joint coding can explain all Pulfrich phenomena in a unified way (N. Qian & R. A. Andersen, 1997). However, the joint-coding idea has been challenged by recent models (J. C. Read & B. G. Cumming, 2005a, 2005c) that focus on the S shaped functions of perceived disparity in stroboscopic Pulfrich effect (M. J. Morgan, 1979). Here we demonstrate fundamental problems with the recent models in terms of causality, physiological plausibility, and definitions for joint and separate coding, and we compare the two coding schemes under physiologically plausible assumptions. We show that joint coding of disparity and either unidirectional or bidirectional motion selectivity can account for the S curves, but unidirectional selectivity is required to explain direction-depth contingency in Pulfrich effects. In contrast, separate coding can explain neither the S curves nor the direction-depth contingency. We conclude that Pulfrich phenomena are logically accounted for by joint encoding of unidirectional-motion and disparity.

Resonance between electronic and rotational motions in Rydberg states of CaF

The interaction between electronic and rotational motions in the Rydberg states of calcium monofluoride is investigated using multichannel quantum defect theory (MQDT). By examining the partial-ℓ and N + composition of the molecular wavefunctions of successive members of each of the Rydberg series, we show that the nature of the interaction between the motion of the Rydberg electron and the rotational motion of the ion core undergoes complex and non-monotonic changes with increasing principal quantum number n* and total angular momentum N. Resonances between the Kepler motion of the Rydberg electron and the rotational motion of the ion core (the ‘stroboscopic effect’) are observed when the Kepler period is an integer multiple of the rotational period. These resonances result in strong mixing of both the electron orbital angular momentum ℓ and the ion core rotational angular momentum N +. At n* or N values between these resonances, the angular momenta of the electron and ion core subsystems are more nearly conserved. We also find evidence for a second type of resonance, which takes place between the precessional motion of the Rydberg electron and the rotation of the core. The qualitative features of these various dynamical regimes can be explained in terms of the classical frequencies of motion of the electron and ion and the nature of the electrostatic interactions between them. The results presented here provide general insights into the interaction between electronic and rotational motions in both polar and non-polar diatomic molecules.

Long-term persistence of solar active longitudes and its implications for the solar dynamo theory

We present an overview of the observational results related to the existence of long-lived sunspot active longitudes. These are affected by the solar differential rotation. The existence of such migrating active longitudes imposes an important constraint on the dynamo theory. We review different approaches to model non-axisymmetry in solar dynamo models and find that, in principle, plausible mechanisms exist to reproduce the observed non-axisymmetry. The most favorable interpretation is suggested by the ‘stroboscopic effect’, where a quasi-rigidly rotating non-axisymmetric mean field can produce seemingly migrating active longitudes in sunspots. Other scenarios are less favorable but cannot yet be excluded.

All Pulfrich-like illusions can be explained without joint encoding of motion and disparity

In the Pulfrich effect, an interocular time delay results in the perception of depth. Two modified versions, the stroboscopic Pulfrich effect and dynamic visual noise with a delay, are generally explained by postulating an early stage of space/time-inseparable filtering, encoding motion and disparity jointly. However, most disparity sensors in monkey V1 do not show joint motion/disparity encoding, and we recently showed that depth perception in the stroboscopic Pulfrich effect is equally compatible with space/time-separable filtering. Here, we demonstrate that this filtering can be implemented with a population of physiologically plausible energy model units. Similar results are obtained whether the neurons are pure disparity sensors (like most V1 neurons) or joint motion/disparity sensors (like MT). We also demonstrate that the dynamic noise stimulus produces correlations between the activity in pure disparity sensors, and in a separate population of pure motion sensors. These correlations are sufficient to explain the percept. Thus, joint encoding of motion and disparity is not required to explain depth perception in Pulfrich-like stimuli: a brain which encoded motion and disparity in entirely separate neuronal pathways could still experience all of these illusions.

Optical 3-D shape and deformation measurement of rotating blades using stroboscopic structured illumination

An optical method for shape and deformation measurement of a rotating blade, which is based on Fourier transform profilometry FTP and the stroboscopic effect, is proposed and has been verified by experiments. The integrated principles of the method, the process of 3-D phase unwrapping, and the detailed design of the synchronization con- trol unit are discussed. Experimental results on a commercial electric fan prove that FTP can reconstruct the shape of a rotating blade efficiently and reveal its deformation different times clearly by using stroboscopic structured illumination. This method can be used for studying high-speed motion with rapid periodic signals. © 2005 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2127927 Subject terms: Fourier transform profilometry; 3-D shape measurement; stroboscope; dynamic 3-D visualization; structured illumination; phase unwrapping; rotating blade.

Heart rate slowing by If inhibition: therapeutic utility from clinical trials

Myocardial ischaemia results from an excess of myocardial oxygen demand in comparison with available supply. Heart rate is a primary determinant of oxygen demand and thus its reduction is a well-accepted strategy for the prevention of angina pectoris, a highly debilitating symptom of coronary artery disease, but does not usually presage imminent myocardial infarction or death. Currently available drugs that reduce heart rate are commonly associated with adverse effects, which may limit their use in many patients. Therefore, it is important to develop additional alternatives with different pharmacological effects. The inward sodium–potassium-mediated If current of sinoatrial node cell membranes (functionally absent elsewhere in the myocardium) modulates sinoatrial diastolic depolarization rate and, thus, heart rate. Heart rate reduction can be achieved by modulating or blocking this current. Ivabradine, a highly selective If current inhibitor, can reduce heart rate by clinically useful decrements at doses that are devoid of other direct cardiovascular effects and generally are well tolerated. The only dose-related adverse effects are visual (phosphenes, stroboscopic effect, and non-typical blurred vision), which occur in 2–15% of patients receiving 2.5–10 mg orally twice daily, usually are no more than mildly bothersome, are fully reversible spontaneously or with cessation of therapy, and are not associated with retinal damage. Clinical trials involving more than 5000 patients indicate that ivabradine as monotherapy is effective in preventing angina. Effects are seen at doses as low as 2.5 mg twice daily. Preliminary data suggest that when employed at 7.5 or 10 mg twice daily, angina prevention with ivabradine is equivalent to that achieved with atenolol 100 mg daily and with amlodipine 10 mg daily.